1. Technical Field
The present invention relates to a pointer detection apparatus and a pointer detection method for use, for example, with a touch panel. More particularly, the present invention relates to a pointer detection apparatus and a pointer detection method capable of detecting positions of a plurality of pointers according to a capacitive coupling method.
2. Description of the Related Art
As a method for position detection of a pointer used with a touch panel or the like, various sensor methods such as a resistive film method, a capacitive coupling method, and a capacitance method have been proposed. Recently, a capacitive coupling type pointer detection apparatus has been vigorously developed.
As a capacitive coupling method, two types of methods are available: a surface type (Surface Capacitive Type) method and a projection type (Projected Capacitive Type) method. The surface capacitive type method is applied, for example, in an ATM (Automated Teller Machine) and so forth, and the projected capacitive type method is applied, for example, in a portable telephone set and so forth. In both methods, a variation of a capacitive coupling state between a sensor electrode and a pointer, such as a finger or a capacitive pen, is detected to detect the position of the pointer.
A pointer detection apparatus, in which the projected capacitive type capacitive coupling method is applied, detects a variation of a capacitive coupling state between a pointer and a plurality of electrodes disposed in parallel with each other. The pointer detection apparatus includes the electrodes arranged in a predetermined conductor pattern on, for example, a transparent substrate such as a glass substrate or a transparent film, and detects a variation of a capacitive coupling state between a pointer and the electrodes when the pointer approaches the electrodes. For a pointer detection apparatus in which such method as described above is applied, various techniques have been proposed, for example, in Japanese Patent Laid-Open No. 2003-22158 (hereinafter referred to as Patent Document 1), Japanese Patent Laid-Open No. Hei 9-222947 (hereinafter referred to as Patent Document 2) and Japanese Patent Laid-Open No. Hei 10-161795 (hereinafter referred to as Patent Document 3). In Patent Document 1, a technique is disclosed wherein a code-division multiplexing method that uses orthogonal spread codes is applied in a multi-user touch system. In Patent Document 2, a coordinate inputting apparatus which uses a pseudorandom code (PN code) is disclosed. Further, in Patent Document 3, a pen as a pointer to be used in a capacitive type coordinate apparatus is disclosed.
Recently, a pointer detection apparatus has been proposed, in which a method called cross-point capacitive coupling method is applied. In the cross-point capacitive coupling method, a plurality of electrodes are disposed both in an X direction and a Y direction to form conductor patterns, and a capacitive coupling state at each of the cross points is measured, at which the electrodes orthogonally cross each other. When a finger approaches a cross point, the capacitive coupling state at the cross point varies, and thus the position of the finger can be detected by detecting the coordinates of the cross point whose capacitive coupling state exhibits a variation.